Silicon as a semiconductor: Silicon carbide would be much more efficient

Silicon as a semiconductor: Silicon carbide would be much more efficient
At the interface between silicon dioxide and silicon carbide, irregular clusters of carbon rings occur, which disturb the electronic function. Credit: Universität Basel, Departement Physik/Swiss Nanoscience Institute

In power electronics, semiconductors are based on the element silicon—but the energy efficiency of silicon carbide would be much higher. Physicists of the University of Basel, the Paul Scherrer Institute and ABB explain what prevents the use of this combination of silicon and carbon in the scientific journal Applied Physics Letters.

Energy consumption is growing across the globe, and sustainable energy supplies such as wind and are becoming increasingly important. Electric power, however, is often generated a long distance away from the consumer. Efficient distribution and are thus just as crucial as transformer stations and power converters that turn the generated direct current into alternating current.

Huge savings are possible

Modern must be able to handle large currents and high voltages. Current transistors made of for are now mainly based on silicon technology. Significant physical and chemical advantages, however, arise from the use of SiC over silicon: in addition to a much higher heat resistance, this material provides significantly better energy efficiency, which could lead to massive savings.

It is known that these advantages are significantly compromised by defects at the interface between silicon carbide and the insulating material silicon dioxide. This damage is based on tiny, irregular clusters of carbon rings bound in the crystal lattice, as experimentally demonstrated by researchers led by Professor Thomas Jung at the Swiss Nanoscience Institute and Department of Physics from the University of Basel and the Paul Scherrer Institute. Using atomic force microscope analysis and Raman spectroscopy, they showed that the defects are generated in the vicinity of the interface by the oxidation process.

Experimentally confirmed

The interfering carbon clusters, which are only a few nanometers in size, are formed during the oxidation process of silicon carbide to silicon dioxide under high temperatures. "If we change certain parameters during oxidation, we can influence the occurrence of the defects," says doctoral student Dipanwita Dutta. For example, a nitrous oxide atmosphere in the heating process leads to significantly fewer carbon clusters.

The experimental results were confirmed by the team led by Professor Stefan Gödecker at the Department of Physics and Swiss Nanoscience Institute from the University of Basel. Computer simulations confirmed the structural and induced by graphitic carbon atoms as observed experimentally. Beyond experiments, atomistic insight has been gained in the generation of the defects and their impact on the electron flow in the semiconductor material.

Better use of electricity

"Our studies provide important insight to drive the onward development of field-effect transistors based on silicon carbide. Therefore we expect to provide a significant contribution to the more effective use of electrical power," comments Jung. The work was initiated as part of the Nano Argovia program for applied research projects.


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More information: Applied Physics Letters (2019). DOI: 10.1063/1.5112779
Journal information: Applied Physics Letters

Citation: Silicon as a semiconductor: Silicon carbide would be much more efficient (2019, September 5) retrieved 15 September 2019 from https://phys.org/news/2019-09-silicon-semiconductor-carbide-efficient.html
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Sep 05, 2019
The article does not mention that silicon carbide power transistors are already being sold, and have been for many years. This, though, appears to be a welcome improvement to the manufacturing process

Sep 06, 2019
The article does not mention that silicon carbide power transistors are already being sold, and have been for many years. This, though, appears to be a welcome improvement to the manufacturing process
MOSFET (either planar or FinFET) transistors for CPUs, SoCs or GPUs, which is the most important application, do not yet exist (at least not commercially, there might exist some custom made SiC based CPUs for some military applications that require high heat endurance, such as ICBMs).
SiC is used for power electronics largely in the form of JFETs, bipolar transistors, thyristors, and even MOSFETs but for high power (1200 V or so) switching applications.

Generally it is being used for high power and high heat stuff. It has 2.5 to 3.3 times -depending on its crystal structure- the thermal conductivity of silicon, a bit less or higher even than copper and silver, so it can literally "take the heat". Silicon has a temperature limit of 150 °C.

Sep 06, 2019
The other problem with Si transistors is that the material has a negative differential temperature coefficient, so when the transistors becomes to hot they will go into thermal runaway and break down. SiC has a better properties in that regards, Ge worse. (Though SiGe is often used similar to the image here with thin interface layers in Si BiCMOS technology.)

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